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Old November 19th, 2008, 09:45 PM   #1
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Default 302 carb probs

I have a 302 with an eldelbrock 600 carb and performer intake. This motor came out of a bronco and was running when I pulled it. I put it in a yj and now it will idle but has major hick-ups when I try to drive it. Its back firering throu the carb. The timming is good and The plugs are good too. Also I can only pull about 15lbs of vac. I need some help! Pulling my hair out trying to get this right. Any advice would help
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Old November 19th, 2008, 09:59 PM   #2
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Sounds like lack of fuel. It could be a plugged filter, bad fuel pump or the bowl of the carb could be plugged up with oxidation or varnish.
Start by making sure you have plenty of fuel getting to the carb. Disconnect the fuel line and put it into a container then see how well the pump fills the container.
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Old November 19th, 2008, 10:06 PM   #3
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start by checking your fuel pressure and post results here.
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Old November 19th, 2008, 10:13 PM   #4
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Nah, It's not fuel injected. If it were spraying a steam of fuel though the aircleaner then fuel pressure would be an issue. This is far more a flow issue.
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Old November 19th, 2008, 10:31 PM   #5
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Quote:
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Nah, It's not fuel injected. If it were spraying a steam of fuel though the aircleaner then fuel pressure would be an issue. This is far more a flow issue.
I know its carbed..4-6 psi is the range, 5.5 optimum. Too low pressure will drain the float bowls under a load. Also check for a kink in the fuel line down near the fuel pump or anywhere where the line is routed.
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Old November 19th, 2008, 10:35 PM   #6
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On a carburated engine it is a huge waste of time to test fuel pressure. If the fuel pump is pumping a good amount of fuel out, you have enough pressure. Much easier to do a flow test and you can do a visual test of the quality of the fuel at the same time.
15 lbs of vacuum is defiantly a problem!!!!!! 15 inches of vacuum could be a vacuum leak which, would give you the same symptoms as lack of fuel. Check the base gasket.

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Old November 19th, 2008, 10:45 PM   #7
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On a carburated engine it is a huge waste of time to test fuel pressure. If the fuel pump is pumping a good amount of fuel out, you have enough pressure. Much easier to do a flow test and you can do a visual test of the quality of the fuel at the same time.
Waste of time? Fuel pressure is the first thing you wanna make sure is correct before going deeper into diagnosing. Go readup on these carbs more or go tune one for yourself..check out the tech vids on the website.
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Old November 19th, 2008, 10:55 PM   #8
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Dude, it takes twice as long to do a pressure test on a carburated engine as it does to do a flow test. No tester needed. Just cut the top of a pop bottle, clean it out and you have yourself all the tester you need.
I have been tuning carburated engines for over 20 years. I own 6 of them right now and I am the only person that works on my vehicles. I am a michigan cerified master auto mechanic. I also have the 9th certification which is "pre-'73 vehicles".
I have custom built many carburators that outperform anything you can buy. I am not one of those feable minded people that say "holley carbs are junk" I know better.
On a fuel injected vehicle you start with fuel pressure then test flow second as it is harder to test flow then pressure.

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Old November 19th, 2008, 11:15 PM   #9
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to each his own
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Old November 20th, 2008, 12:13 AM   #10
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Quote:
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On a carburated engine it is a huge waste of time to test fuel pressure. If the fuel pump is pumping a good amount of fuel out, you have enough pressure. Much easier to do a flow test and you can do a visual test of the quality of the fuel at the same time.
15 lbs of vacuum is defiantly a problem!!!!!! 15 inches of vacuum could be a vacuum leak which, would give you the same symptoms as lack of fuel. Check the base gasket.
I only pull about 13-15" of vacuum @ 850 rpm on my 5.0 HO. If the engine in question has a different cam than factory it may produce lower vacuum without a leak.

Did anything change with the carb/engine during the swap besides the sheet metal that surrounds it? How long did it set before the swap was completed? If it sat for a while it may have gummed one of the primary jets or need valves a little. Float height might also be an area of concern, even if it ran good in the other vehicle, its new home may have a different slope to the intake and might make the previous float level too low.
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Old November 20th, 2008, 07:05 AM   #11
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I only pull about 13-15" of vacuum @ 850 rpm on my 5.0 HO. If the engine in question has a different cam than factory it may produce lower vacuum without a leak.

Did anything change with the carb/engine during the swap besides the sheet metal that surrounds it? How long did it set before the swap was completed? If it sat for a while it may have gummed one of the primary jets or need valves a little. Float height might also be an area of concern, even if it ran good in the other vehicle, its new home may have a different slope to the intake and might make the previous float level too low.
dose have a slightly larger angle.
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Old November 20th, 2008, 07:09 AM   #12
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start by checking your pfuel pressure and post results here.
5.5 psi throu regulator. Also have elec. fule pump moving 90 lbs per hour. at first I was getting too much gas, and flooding out. Put a new reg on and fixed that. I will check for vac leaks tonight. thanx i will post results
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Old November 20th, 2008, 09:33 PM   #13
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There may be a filter just inside the inlet of the carb, changing bodies could have got some junk in it. It probably isn't a vacuum leak concidering it ran good before. It still could be contamination in the float bowl as swapping the motor around could have stirred up some junk.
If it does have a healthy cam in it 15" would be ok.
The engine angle is a good point as well, I didn't think of that.
Another thing could be the accelerator pump, if it sat for a while the pump could have dried up. Easy way to check that is to look down the throat of the carb while the engine is NOT running and hit the throttle. If both squirters are shooting out an even stream then that is not your problem.
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Old November 20th, 2008, 09:52 PM   #14
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both squirt good. I will check the filters. If the angle is the prob, what can I do to fix it? I am obviously not a carb guy but i can turn wrenches
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Old November 20th, 2008, 09:57 PM   #15
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I only pull about 13-15" of vacuum @ 850 rpm on my 5.0 HO. If the engine in question has a different cam than factory it may produce lower vacuum without a leak.

Did anything change with the carb/engine during the swap besides the sheet metal that surrounds it? How long did it set before the swap was completed? If it sat for a while it may have gummed one of the primary jets or need valves a little. Float height might also be an area of concern, even if it ran good in the other vehicle, its new home may have a different slope to the intake and might make the previous float level too low.
The engin sat for five months, I was forced to put the engin at a slightly larger angle to clear my front driveshaft and axle. It dosent look like much more, but I know this could be a prob. If so, what can i do to test?
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Old November 20th, 2008, 10:03 PM   #16
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You will need to pull the top of the carb off. Once you have the screws out, pull up carefully and slowly. On the edelbrock there are two little plates on top that are sort of tear drop shaped, they have one screw each. Those are the covers for the metering rods. Pull those covers before you pull the carb top. Make sure the pistons aren't seized into place (common problem). If they are, that could be your problem. carefully work them up and down until they move freely. You should be able to push them down with little pressure and they should spring right back up.
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Old November 20th, 2008, 10:26 PM   #17
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here is a link the the electronic owners manual for edelbrock carbs. It will go thru all the proper adjustment procedures as well as a trouble shooting section that may give some insight.

http://static.summitracing.com/globa...405_manual.pdf
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Old November 20th, 2008, 10:30 PM   #18
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You may want to give it a good thourough cleaning while you have the top off of it. Even if you can't see anything gunky in there, it doesn't take much to screw up the metering of the jets. You will need to pull the carb off of the intake for this to avoid getting any junk into the intake itself.

One other thing to consider while you have it apart would be to install the offroad needle and seat set. It is a new needle valve that is spring loaded to avoid flooding over rough terrain. (obviously this will only benefit you if this is an offroad toy)
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Old November 20th, 2008, 10:38 PM   #19
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Quote:
Originally Posted by DeRanged mudder View Post
You will need to pull the top of the carb off. Once you have the screws out, pull up carefully and slowly. On the edelbrock there are two little plates on top that are sort of tear drop shaped, they have one screw each. Those are the covers for the metering rods. Pull those covers before you pull the carb top. Make sure the pistons aren't seized into place (common problem). If they are, that could be your problem. carefully work them up and down until they move freely. You should be able to push them down with little pressure and they should spring right back up.
be sure to do this first to avoid bending the metering rods, also when you go back together they will be the very last part you install.

also, look at the accelerator pump plunger seal, if this is dry, cracked, or overly flexible you may be getting blowby and not the correct boost when applying throttle. There is also a specific location for the lever based on carb model, and a measurement tolerance for travel at the maximum end of the travel.

Here is one more link to some info on these carbs. This comes from the rebuild kit for these carbs. http://static.summitracing.com/globa...s/edl-1477.pdf
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Old November 21st, 2008, 03:30 AM   #20
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i dont know but ive been having the same problem, except it wont even idle, just turn over and hiccup
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